The industry standard method of refuelling large diesel powered equipment in the mining, railway, and earthmoving industries has incorporated dry-break fluid couplings designed to transfer diesel fuel from dispensing point into the fuel tank onboard the equipment. This transfer is often done at relatively high flowrates and within a sealed fuel delivery system. The couplings used to engage the dispensing point with the equipment consist of a female coupling typically at the dispensing point—termed the nozzle—and a male coupling onboard the equipment—termed the receiver. The nozzle typically incorporates a manual operation handle (open/closed), and modern nozzles also incorporate an automatic shut-off mechanism. This automatic mechanism is sensitive to fluid pressure passing through the mating nozzle and receiver, and activates at a preset pressure to automatically close the nozzle and hence terminate the transfer of fuel. This pressure generated in the fuel is typically from the pressurisation of the fuel tank, once it is filled.
Large equipment often incorporate fuel tanks of several thousand litre capacity, and are located on the equipment often several metres from ground level. To facilitate refuelling of the equipment from ground level, the fuel receiver is often situated in a position readily accessible to the refuelling operator and is linked to the fuel tank by a length of fixed pipe and/or flexible hose. Access from ground level has obvious occupational safety and time efficiency benefits.
The mechanical engagement of the nozzle and receiver creates wear between mating surfaces and sealing elements (fluid seals). Nozzles are often routinely removed from active use for the purpose of maintenance to replace damaged or otherwise faulty components. Replacing the receiver installed on equipment is often more difficult, and unless a separate fluid isolation valve exists between the receiver and the tank, the tank must be drained of fuel to a level below the receiver before the receiver can be replaced. This is costly and creates the risk of fuel spillage and subsequent environmental damage.
Drainage of fuel from the fuel tank via the receiver can typically occur in two ways:    (i) The receiver seal is damaged, or the receiver itself suffers impact with another object causing the receiver to fracture; or    (ii) Fuel is pilfered from the tank.
Many thousands of litres of fuel can be lost if no means of back-flow prevention exists between the receiver and the tank.
There are two (2) known fuel receiver products which have an integral back-flow prevention mechanism designed to prevent the drainage of fuel from the tank via the receiver. One such product employs a simple disc style check valve mechanism which is opened by fluid pressure acting directly onto the disc, and is closed by the action of a spring. The front receiver body of the product can be changed out without the need to drain the tank. Another such product is designed so that the second back-flow prevention valve is directly (mechanically) opened by the displacement of the first poppet valve. The principal role of the second valve in this product is to prevent the backflow of fuel during removal (changeout) of the receiver body.